The tear film and subjacent ocular surface will be studied in order to advance our understanding of the pathogenesis of drying of the ocular surface and in order to improve our ability to diagnose, assess and treat those disorders where ocular surface drying is clinically significant. The eyes of NZB/NZW F1 hybrid mice, a model for Sjogren's Syndrome, will be followed over time with morphological studies and the recently developed micromethod of tear osmolarity determination as these animals develop keratoconjunctivitis sicca (KCS). The effect of hypertonic solutions infused onto the ocular surface of cat eyes will be studied morphologically. Tear film osmolarity kinetics will be studied in KCS patients after the instillation of saline solutions ranging in tonicity from hypotonic to isotonic. A double-masked study will compare the therapeutic value of isotonic saline and a hypotonic saline solution of selected tonicity. The effect of an isotonic or slightly hypotonic saline eye cup bath and the effect of punctal occlusion on tear film osmolarity and Rose Bengal staining in KCS patients will be studied in separate protocols. Mucus-stimulating substance in the tears of KCS patients, as well as NZB/NZW F1 hybrid mice, will be compared with controls using the invertebrate Sipunculus Nudus urn cell assay system. Corneal exposure will be examined in Graves' disease and Bell's palsy in order to investigate the possible etiologic roles of elevated tear film osmolarity and dry spot formation in the pathogenesis of ocular surface disease.